There are many different types and styles of sawmills. As generally shown in FIGS. 1 and 2, a certain type of sawmill 10 employs a band saw 12, mounted on a carriage 14 that is capable of moving back and forth in a reciprocating motion along a track 16. Carriage 14 is moved back and forth by conventional means, such as a cable 14a attached at each end to a respective end of the carriage, driven by a prime mover 14b such as a hydraulic or electric motor, and reeved about a cable drum 14c and a remote cable tensioning wheel 14d before terminating at the carriage. While the cable arrangement is shown positioned at the right side of the carriage 14 for ease of depiction, it may just as well be positioned at the left side of the carriage.
The band saw 12 includes a continuous loop blade 18, which is driven by, among other things, a motor 20 and reeved about pulleys 22. In operation, a log 24 is held on a cradle or bunk 26 and oriented generally parallel to the track 16 and the direction of movement of the band saw 12. The bunk 26 holds the log 24 in proximity to the band saw blade 18, and has the capability to move the log toward the band saw 12, so at least some portion of the log extends beyond the bunk. Thus the band saw 12 is enabled to cut a segment 28 (FIG. 2) off the log, whether that segment be a slab (most likely waste) or a board or a plank. Once cut, each segment 28 ends up on a conveyor 30, supported on a conveyor support 32, to be conveyed to another destination for further processing. As the segment 28 is cut, the segment first contacts and drops onto a stationary shear rail 34, which is mounted to conveyor support 32 as is the conveyor 30, and extends outward from the side of the conveyor toward the uncut log 24, at an angle from close to the conveyor upward toward the log, so as to act as a ramp or funnel, the idea being that the segment will slide along that angle and end up on the conveyor, face up (that is, cut side down).
As can be seen in FIG. 2, a small gap 36 necessarily exists between the shear rail 34 and the band saw blade 18, as there must be a clearance between them in order for the blade to pass back and forth as it cuts the log 24. When the segment 28 is cut from the log 24, there is a chance that the segment could fall into that gap 36, and thereby become hung up. There are times when this hangup of the segment 28 in the gap 36 results in the serious problems for the sawmill, sometimes requiring a temporary shutdown so that the hangup can be cleared. More often, the edge of the segment 28 catches in the gap 36 and then flops over so that the fresh cut side 38 of the segment is oriented upward (the undesirable “face down” position, which is the opposite of the desired “face up” orientation referred to above) on the conveyor, as shown in FIG. 2.
This invention relates to improvements to the apparatus described above and to solutions to some of the problems raised or not solved thereby.